This invention concerns a method and apparatus for generating a low-sulfur reducing gas by the gasification of carbonaceous fuel in a molten iron bath. Fuel, oxygen and a slag former are injected into the molten metal bath through the bottom of the bath-containing vessel. The reaction within the vessel is cooled by the injection of a gaseous coolant which is recycled spent top gas from a direct reduction furnace, steam or a mixture thereof.
The present invention is an improvement to German OLS No. 27 50 275, which teaches the generation of a reducing gas in a molten metal bath. The known gasifier is noted for its refractory wear. The present invention alleviates the refractory wear problem by maintaining the bath temperature of the gasifier at a lower level. This is achieved by injecting a coolant into the molten metal bath to cool the reaction.
Sanzenbacher et al. U.S. Pat. No. 4,238,226 and Scarlett et al. U.S. Pat. No. 4,248,626 both describe methods for producing gas for direct reduction and the melting of direct reduced iron in a chamber containing a molten metal bath. No coolant is used in either of these processes because the melting of the direct reduced iron maintains the temperature of the molten metal bath in the desired range.
The present invention also provides a well-balanced reducing gas for the direct reduction of iron. This is achieved by maintaining the operating temperature of the molten bath gasifier above the iron-carbon eutectic point.
In the direct reduction of iron oxide to metallized iron in a shaft furnace, the reacted top gas is superheated and must be cooled immediately upon removal from the furnace. The present invention utilizes this superheat to calcine lime for sulfur removal from the shaft furnace.